Boot Insert

ABSTRACT

A low friction boot insert 1 that is positioned around the lower leg surrounding a sock 2 and on the inside of a boot 4 such as those worn for skiing. Rotational movement 5 and longitudinal movement 6 of the skin 3 relative to the boot surface is minimised by reducing friction at the interface of the insert and boot or the interface of the insert and sock or both. The reduction in friction transferred to the interface between sock and skin helps to reduce the chafing of the skin which can cause blisters or sores.

The present invention relates to a ski boot insert and particularly, though not exclusively, a low friction ski boot insert positionable around the lower leg of a user to reduce the incidence of blisters and sores caused by friction on the skin transferred via shear forces across boot and sock interfaces.

Skiing while wearing conventional ski socks and ski boots involves repeated transfer of shear forces from ski boot to user's skin due to movement in both the rotational and longitudinal directions of the ski boot relative to the user's leg. This transfer occurs as shear forces are transferred by friction across the inner surface of the ski boot and in turn across layers of sock fabric onto the user's skin. For many skiers, this repeated friction on the skin of the lower leg can result in painful blisters or sores. The problem becomes even more prevalent with exacerbating conditions such as when wearing relatively heavy skis or when skiing in heavier and deeper snow. In severe cases the repeated friction transferred to the sock and skin interface can cause severe pain, may result in blisters and sores and can even scar surface tissue on the leg. In many cases the pain and tissue damage can prevent the person from continuing to ski. Tissue damage is particularly prevalent around the shin and outer calf regions where the leg is subject to a great deal of the forces and movements against the ski boot. Additionally, some ski boots have inner surfaces with protruding lips between the forward and rear inner-boot sections where the effects of friction are exacerbated by repeated grabbing or pinching of the skin between the lips.

Fitted or moulded boots can alleviate the problem to some degree by ensuring a more equal distribution of forces acting around the leg and thus reduce chafing on concentrated areas of the leg. Additional cushioning and padding can also serve to alleviate more of the problems related to compressive forces acting on the user's shin. Socks with a better fit or moisture wicking properties can also help to address other variables which exacerbate the effects of repeated chafing. However, often these well-established and conventional solutions are inadequate means to control the repeated transfer of shear, rather than compressive, forces from ski boot via sock fabric to skin which is the root cause of many blisters and sores.

In addition, a variety of socks and sock or boot insert devices have been developed, patented or sold commercially which have contributed to improved user comfort and reduced friction experienced by the user's skin. Prior art predominantly concerns inventions including one or more of three methods to reduce friction.

Firstly, a number of double- and triple-ply socks have been developed to reduce friction at the skin by reducing shear forces across multiple sock surfaces. Low friction fabric surfaces have also been developed for integration into sock and/or boot surfaces to aid in the reduction of frictional forces. U.S. Pat. No. 4,571,960 and U.S. Pat. No. 6,108,820 describe low coefficient of friction polymers such as nylon yarn woven into one of the two plies of a double-ply sock design. Patent US2008264512 describes a material formed from 2 plies combined at a specific orientation and with specific weaves to permit the 2 surfaces to glide in relation to one another. Patent U.S. Pat. No. 5,829,057 goes further incorporating low friction fabrics or chemicals into specific regions of the fabric. In particularly high-shear conditions when skiing, however, double- and triple-ply socks formed from layers of fabric or treated fabric often cannot reduce shear forces being transferred to the skin to a sufficient degree to prevent blisters and sores from developing. Multi-ply socks are also disadvantageous in that they add bulk to the user's foot region and the non-rigid nature of such fabrics in a multi-ply format can lead to bunching or grabbing of the fabrics within ski boots that can be uncomfortable or even exacerbate the effects of friction on the skin.

Secondly, several patents have developed padding or cushioning solutions which reduce the effects of compressive and tensile forces through absorption. These include patents WO2008011686, U.S. Pat. No. 4,066,074 and NL9001115 which focus on improved padding around the shin area as well as inventions such as US2007043316 which are adhered as low-friction padding a to a region of skin or inside surface of shoe/boot to alleviate friction. These solutions are particularly effective in reducing the effects of “shin bang” whereby the principle damage to the skin is caused by the front of the shin repeatedly hitting the frontal inner ski boot surface or other situations where skin damage is caused primarily by compressive and tensile forces acting on the leg. The benefits of these devices reside primarily in a padding element which absorbs such compressive and tensile forces acting perpendicularly between ski boot and shin rather than reduction of shear forces resulting from rotational and longitudinal movements of the leg relative to the ski boot. As a result, they are effective measures to prevent shin bang and other ailments relating to compressive forces but do not adequately reduce the shear forces which is the concern of the present invention.

Thirdly, a number of patents have described low-friction insert layers which reduce the transfer of friction to the skin. Such insert layers can be formed from a plastic or similar semi-rigid material shaped to fit around an area of the foot or leg and reduce shear forces being transferred from an outer surface relative to the insert to the skin on the inner side of the insert. Among others, patents US2011289657 and US2011289657 relate to a reduction of friction on and around the sole of the foot, rather than the lower leg area, which is the concern of the present invention. U.S. Pat. No. 5,615,418 describes a three-part footwear system including a friction isolation layer made from a semi-rigid material such as vinyl, satin cloth or mylar. However, this patent specifically concerns a friction isolation layer as part of a three part system including an inner and outer layer of fabric disposed either side of the insert. The described sandwich structure comprising double fabric plies of this invention presents similar disadvantages as other multi-ply socks in that bulk is added to the sock and bunching of the fabric may occur. Further, the usefulness of this type of insert is limited by the need to use it with specially-configured inner- and outer-socks.

Previous approaches to managing the blisters and sores caused by frictional forces around the lower leg during skiing have had varied success, or have focused on reducing compressive rather than shear forces. Thus, there is a need to provide a simple and effective means to reduce primarily shear forces from the skin of the lower leg arising from rotational and longitudinal movements of the ski boot relative to the user's leg without the use of multi-ply fabric socks.

To address these needs, the present invention proposes a low coefficient of friction insert which is wrapped around a user's lower leg between sock and ski boot inner surface such that it surrounds the region between ankle and mid-calf, or a portion thereof. Said insert takes a flat form before application and is constructed from a semi-rigid but deformable material with a low coefficient of friction on one or both sides.

Transfer of shear forces to the skin arising from movement of the ski boot's inner surface relative to the user's leg are minimised by reducing friction at the insert surfaces. This results in a decoupling of shear forces acting on the user's skin relative from the ski boot and therefore reduced chafing of the skin. As opposed to a variety of prior art which focuses on absorbing the compressive forces between shin and ski boots the present invention reduces friction arising from shear forces resulting from the rotational and longitudinal movements of the ski boot relative to the user's leg.

This is achieved with the application of a semi-rigid low-friction insert between a conventional single-ply ski sock and ski boot, avoiding the disadvantages of multi-ply socks such as added bulk and bunching of fabrics. The resulting advantage of these factors is a reduced incidence of painful blisters and sores on users and thus the enjoyment of longer periods of skiing without experiencing painful skin irritation or damaged tissue.

According to a first aspect of the present invention, there is provided a ski boot insert for positioning around a user's lower leg between a sock outer surface and a boot inner surface to reduce the transfer of friction to the skin of a user arising from movement of the boot; the boot insert comprising a deformable panel having smooth major surfaces; two panel ends; and mutually interlockable elements extending from each panel end; wherein each smooth major surface has a static coefficient of friction against cotton fabric of 0.5 or less.

Optionally, the deformable panel has an arcuate-oblong shape when in a non-deformed condition.

Advantageously, such a shape allows the deformable panel to more easily conform to user's legs which tend to increase in girth with increasing distance from the ankle. More particularly, a wide range of leg girths can be accommodated. In a non-deformed condition the panel could have dimensions ranging from a minimum of 200 mm and maximum 400 mm in length and minimum of 80 mm and maximum 240 mm in width.

Optionally, the shorter lateral ends of the arcuate-oblong shaped deformable panel are convexly curved.

Advantageously, such a shape facilitates a degree of overlap of the shorter lateral ends when in place on a user's leg

Advantageously, the mutually interlockable elements maintain the lateral ends of the deformable panel in position, conform closely to the shape of the user's leg and inhibit twisting or other unwanted relative movement of the lateral ends.

Optionally, the deformable panel is formed from a plastic or composite material having a thickness of between 0.1 mm and 4.0 mm.

Advantageously, the deformable panel may be manufactured from commercially available materials using simple pressing and surface treating processes and therefore has a relatively low cost.

Optionally, aeration apertures extend through the deformable panel between the major surfaces.

For example, the provision of small holes or grooves across the surface can be used to improve aeration properties and allow moisture to be wicked away from the skin.

According to a second aspect of the present invention, there is provided a boot insert assembly comprising: (i) a ski boot insert according to the first aspect; (ii) a sock; and (iii) a strip of relatively high friction elastomeric material; wherein said elastomeric material is for positioning around a user's leg between said sock's outer surface and a boot's inner surface, and above said deformable panel.

According to a third aspect of the present invention, there is provided a boot insert assembly comprising: (i) a ski boot insert according to the first aspect; and (ii) a sock; wherein at least part of the sock is provided with a second ply defining a space within which the deformable panel can be accommodated.

According to a fourth aspect of the present invention, there is provided a boot insert assembly comprising: (i) a ski boot insert according to the first aspect; (ii) a boot; and (iii) a sock; wherein at least part of an upper portion of said sock and at least part of an upper portion of said boot are provided with releasable fastening means.

The assemblies of the second, third and fourth aspects each provide means for avoiding or at least limiting upward movement of the deformable panel during use.

According to a fifth aspect of the present invention, there is provided a method of reducing the transfer of friction between a boot and a user's skin comprising the steps of: (i) providing a ski boot insert having a deformable panel according to the first aspect; (ii) positioning said deformable panel around a user's lower leg between a sock outer surface and a boot inner surface; and (iii) interlocking the elements extending from each panel end.

Optionally, the step of fitting said deformable panel to the shape of a user's lower leg involves heating the deformable panel and moulding it around the user's sock and leg or an object with a similar shape.

It will be appreciated that a comfortable fit of the deformable panel around the contours of the user's leg will contribute further to a reduction in friction transfer. Whilst heat-assisted moulding of an appropriate material may be employed, this may be achieved in other ways.

Optionally, the method includes the further step of positioning a strip of relatively high friction elastomeric material around a user's leg between an outer surface of the sock and an inner surface of the boot, and above said deformable panel.

Alternatively, the method includes the further step of providing a sock having a second ply defining a space within which the deformable panel can be accommodated.

Alternatively, the method includes the further step of providing releasable complementary fastening means on at least part of an upper portion of the sock and at least part of an upper portion of the boot.

Embodiments of the present invention will now be described by way of example only, with reference to the following diagrams, in which:

FIG. 1 shows a cross-sectional view of a user wearing an insert between sock and ski boot and differentiates between the principal forces acting between a ski boot and a user's lower leg.

FIG. 2 shows a cross-sectional view of a user wearing an insert according to the present invention which differs from that illustrated in FIG. 1 insofar as the insert is shaped to include extending elements which substantially interlock or overlap where the ends of said insert meet.

FIG. 3 shows a cross-sectional view of a user wearing an insert according to an alternative embodiment of the invention where the insert is kept in place by applying a band of high-friction material around the circumference of a user's sock just above the insert.

FIG. 4 shows a cross-sectional view of a user wearing an insert according to a further alternative embodiment of the invention where the insert is placed between an inner and outer sock ply, all situated within a ski boot.

FIG. 5(a) shows an enlarged view of the corresponding layers with a graphical representation of the magnitude of shear forces being transferred from ski boot surface to skin for a user wearing a conventional sock and ski boot as represented in FIG. 5(b).

FIG. 6(a) shows an enlarged view of the corresponding layers with a graphical representation of the magnitude of shear forces being transferred from ski boot surface to skin for a user wearing an insert between sock and ski boot as represented in FIG. 6(b).

FIG. 7 shows a plan view of a low friction insert laid out flat and before wrapping around a user's leg.

FIG. 8 shows a plan view of an insert according to the present invention which differs from that illustrated FIG. 7 insofar as the insert is shaped to include extending elements which substantially interlock or overlap where the ends of said insert meet after wrapping around a user's leg.

FIG. 9 shows a perspective view of a low friction insert as it is being positioned but before it is wrapped around a user's leg.

FIG. 10 shows a low friction insert once positioned around a user's leg and before being fitted within a ski boot.

In FIG. 1, an insert 1 is placed around the lower leg to substantially surround a user's sock 2 which is in turn in contact directly with the user's skin 3 and all of which are worn within a ski boot 4. The insert is positioned around a portion of the lower leg between ankle and upper calf or a portion thereof in order to have a freedom of rotation around and longitudinal movement along the axis of the leg to substantially reduce shear forces being transferred from ski boot to the user's skin via the sock. The insert may be formed from a strip of deformable material wrapped around the user's leg whereby the ends meet to substantially surround the lower leg.

The insert 1 is intended to substantially reduce friction arising from shear forces acting in the rotational direction 5 around the axis of the extended leg as well as shear forces acting in the longitudinal (i.e. upward/downward) direction 6 relative to the extended leg. However, the reduction or absorption of compressive and tensile forces 7 is not a primary concern of the present invention.

The insert is formed from a thin layer of semi-rigid deformable material such as a plastic or a composite with low friction surfaces on one or both sides. The low friction surface or surfaces reduce shear forces acting at the user's skin by reducing friction at either the interface between ski boot inner surface and insert outer surface or at the interface between insert inner surface and sock outer surface or both.

The insert may incorporate small holes or channels to improve aeration of the skin surface so that moisture from sweat collecting at the user's skin is wicked away through said holes or channels.

The insert is shaped to include extending elements or fingers which substantially interlock or overlap where said insert ends meet after being wrapped around the leg, as illustrated in FIG. 2.

FIG. 3 shows an alternative embodiment in which a band of material is placed above the insert and displaced between the sock and the boot to prevent the insert moving vertically out of the intended position. Said bands of material may be attached to either the sock outer surface, the boot inner surface, or to both. These bands may be formed from any material which substantially impedes unwanted movement of the insert such as a rubber, sticky rubber-like material or a plastic. Alternatively, the insert may be kept in position by the use of a temporary attachment between sock and ski boot inner or outer surface such as bands of hook and loop fastener tape positioned between the ski sock and boot surface or a strap which is tightened around the outside of the ski boot after the ski fabric has been extended over it.

FIG. 4 shows a further alternative embodiment in which the sock and insert are surrounded by another layer of sock fabric. This fabric may be an additional single sock worn on top of the skin-contacting sock as represented here. Alternatively, it may be a second sock ply attached to the skin-contacting sock either below or above the position of the insert. 

1. A ski boot insert for positioning around a user's lower leg between a sock outer surface and a boot inner surface to reduce the transfer of friction to the skin of a user arising from movement of the boot; the boot insert comprising a deformable panel having smooth major surfaces; two panel ends; and mutually interlockable elements extending from each panel end; wherein each smooth major surface has a static coefficient of friction against cotton fabric of 0.5 or less.
 2. A ski boot insert according to claim 1, wherein the deformable panel has an arcuate-oblong shape when in a non-deformed condition.
 3. A ski boot insert according to claim 2, wherein the shorter lateral ends of the arcuate-oblong shaped deformable panel are convexly curved.
 4. A ski boot insert according to any preceding claim, wherein the deformable panel is formed from a plastic or composite material having a thickness of between 0.1 mm and 4.0 mm.
 5. A ski boot insert according to any preceding claim, wherein aeration apertures extend through the deformable panel between the major surfaces.
 6. A boot insert assembly comprising: (i) a ski boot insert according to any preceding claim; (ii) a sock; and (iii) a strip of relatively high friction elastomeric material; wherein said elastomeric material is for positioning around a user's leg between said sock's outer surface and a boot's inner surface, and above said deformable panel.
 7. A boot insert assembly comprising: a ski boot insert according to any of claims 1 to 5; and (ii) a sock; wherein at least part of the sock is provided with a second ply defining a space within which the deformable panel can be accommodated.
 8. A boot insert assembly comprising: a ski boot insert according to any of claims 1 to 5; (ii) a boot; and (iii) a sock; wherein at least part of an upper portion of said sock and at least part of an upper portion of said boot are provided with releasable fastening means.
 9. A method of reducing the transfer of friction between a boot and a user's skin comprising the steps of: providing a ski boot insert having a deformable panel according to any one of claims 1 to 5; (ii) positioning said deformable panel around a user's lower leg between a sock outer surface and a boot inner surface; and (iii) interlocking the elements extending from each panel end.
 10. A method according to claim 9, wherein the step of positioning said deformable panel around a user's lower leg involves heating the deformable panel and moulding it around the user's sock.
 11. A method according to claim 9 or 10 comprising the further step of positioning a strip of relatively high friction elastomeric material around a user's leg between an outer surface of the sock and an inner surface of the boot, and above said deformable panel.
 12. A method according to claim 9 or 10 comprising the further step of providing a sock having a second ply defining a space within which the deformable panel can be accommodated.
 13. A method according to claim 9 or 10 comprising the further step of providing releasable complementary fastening means on at least part of an upper portion of the sock and at least part of an upper portion of the boot. 